Centroid Community CNC Support Forum

I am attempting to get my limit switches working for simple safety tripping.

I have X and Y limit switches.
They are wired in series between common and Input 2 on the Acorn board.
Acorn configuration shown in below image.
If I set input 2 to NC I can move the machine, but limit switches do not trip.
If I set input 2 to NO machine says X/Y/Z is tripped and I can't move the machine.

I am not really sure what to do, I have watched Marty's video on this topic and not sure I am on track.

Also if a limit switch trips, how do I move the machine off the tripped switch? I tried reset, but no joy.

Kurt,

Are these mechanical switches or the SB 3 wire inductive? Assuming mechanical and with 3 tabs (com and NC or NO), are you sure that you have them wired in series properly? Check them for continuity when not tripped (closed). You can also use the I/O diagnostic screen to check the state of them (Ctrl+I), and to see if you possibly have INP2 forced on.

To get off a tripped limit, use "Limit Switch Defeat" for a one shot move to get off them.

Sword wrote: ↑Sun Dec 04, 2022 1:30 pm Kurt,

Are these mechanical switches or the SB 3 wire inductive? Assuming mechanical and with 3 tabs (com and NC or NO), are you sure that you have them wired in series properly? Check them for continuity when not tripped (closed). You can also use the I/O diagnostic screen to check the state of them (Ctrl+I), and to see if you possibly have INP2 forced on.

To get off a tripped limit, use "Limit Switch Defeat" for a one shot move to get off them.

I have tried limit switch defeat and no joy.

They are not mechanical, they are from automation direct I had them on my SB before Acorn and they were working as expected.

"Micro Detectors inductive proximity sensor, tubular, 8mm diameter x 29.4mm body, stainless steel housing, NPN, N.C. output, 2mm sensing distance, flush, 7 kHz switching frequency, IP67, 3-pin M8 quick-disconnect."

Below is wiring diagram provided by manufacturer.

Kurt...
Maybe not the instructions on how to fix what you are experiencing, but advice in a different direction. This will allow you to make your machine perform better than it ever could on the SB3 control software.

Use the sensors to home the machine, ON ALL 3 AXES, and use the built-in travel limits to keep the machine off the hard stops. There is no guarantee that prox sensors will work in series, you must connect and test one, then two, then 3 to ensure they will work properly.

Since I always use discreet pins for limit/homing sensors I am not sure that the SB positive end target bolts will work with the Acorn controller, especially in the multi axis, multi direction setup.

Some questions:
Can you trigger each of the sensors with a wrench and see the sensors indicator light change state? If yes, does the assigned input light on the Acorn board change state also? If no you have something wired wrong.

I still recommend adding a sensor to the Z and set up homing and travel limits on all 3 axes like the big boys do, not the "do it cheap and simple" way that SB does.

When you had them working on the ShopBot, did you have them all wired together in series to a single input? Or did you have each sensor on a separate input?

How many sensors do you have connected together in series?

Can you sketch your wiring for how you have connected them together in series?

I agree with Gary.

Use them to home your machine.

And set your travel limits in the software.

That’s how my PRT is setup, works a treat.

Agreed as well, sensors on all three, each to their own input, and use software travel limits. Been working great on my PRS for 4 years.

Gary Campbell wrote: ↑Sun Dec 04, 2022 2:24 pm Kurt...
Maybe not the instructions on how to fix what you are experiencing, but advice in a different direction. This will allow you to make your machine perform better than it ever could on the SB3 control software.
....

Thanks Gary, and for everyone's information, I wired them in series because that is what my Acorn Wiring Diagram had on it. I am a newbie here and did not realize that I could wire them into different inputs.

For Gary Cambell, I did order a Z Axis probe as you suggested and will get that in place now rather than later.

For cnckeith, thanks so much for that diagram, with that and Gary's suggestions, I should be on track to make progress.

This has been a long journey for me trying to get my Acorn Upgrade done, but this forum has been a life saver for me.

Regards,
Kurt